Process for the polymerization of olefins

ABSTRACT

The catalyst used in the process of the present invention is prepared by reacting a heat-resistant metal oxide with a titanium halide to form a reaction product. The reaction product is hydrolized, dried and then reacted with an organoaluminum compound. The unreacted organoaluminum compound is then removed.

I United States Patent [151 3,674,764 Iwasaki et al. 45 J l 4, 1972 [541PROCESS FOR THE POLYMERIZATION 58 Field of Search ..260/94.9 1), 94.9 E,88.2; 0F OLEFINS 252/429 B, 453

[72] Inventors: Koichiro lwasaki; Kazuo Yamaguchi; 5 References CitedHarutaka Kimura; Masayoshi Hasuo, all of Tokyo; Toru Tanaka, Kawaski,all of UNITED STATES PATENTS Japan 2,912,421 11/1959 Juveland et al...260/94.9 D [73] Assignee: Mitsubishi Chemical Industries Limited3,506,633 4/197 Ma u 6i D Filed: June 1971 3,513,150 5/1970 Matsuura eta]. ..260/94.9 D

21 AppLNo; 150 243 Primary Examiner.loseph L. Schofer AssistantExaminer-A. Holler Related US. Application Data Attorney-Bierman &Bierman [63] Continuation of Ser. No. 824,264, May 13, 1969, [57]ABSTRACT abandoned.

The catalyst used in the process of the present invention is [30]Foreign Application Priority Data prepared by reacting a heat-resistantmetal oxide with a titanium halide to form a reaction product. Thereaction product is May 16, 1968 Japan ..43/3276l hydrolizedy dried andthen reacted i an organoaluminum compound. The unreacted organoaluminumcompound is [52] US. Cl ..260/88.2 R, 252/429 A, 252/453, then removed260/93.7, 260/949 D, 260/949 DA, 260/949 E [51] Int. Cl. ..C08t l/42,C08f 1/56, C08f l5/04 14 Claims, No Drawings PROCESS FOR THEPOLYMERIZATION F OLEFINS This application is a streamlined continuationof co-pending Ser. No. 824,264 filed May 13, 1969, now abandoned.

This invention relates to a process for the polymerization of olefins.More particularly, this invention relates to a process for thepolymerization of olefins by using a novel catalyst.

Known heretofore as polymerization catalysts for olefins, especially forethylene polymerization are the so-called Ziegler catalysts as well as anumber of catalysts composed of compounds of the transition metals ofGroups IVa Vla of the Periodic Table and alkyl metal compounds of GroupsIa Illa of the Periodic Table. These catalysts are known to be efiectivefor the polymerization of ethylene at low temperature and low pressure.Further, catalysts composed of compounds of the transition metals ofGroups lVa Via of the Periodic Table and certain alkyl compounds ofmetals of Group Nb of the Periodic Table are known to be effective forthe polymerization of ethylene.

The present inventors have now found that the polymerization of olefinscan be carried out on a commercial scale using a catalyst other than theabove known catalysts. It is therefore an object of this invention toprovide an industrially suitable process for the polymerization ofolefins. The process of the present invention can easily be achieved bythe polymerization of olefins in the presence of a catalyst which hasbeen obtained by reacting a heat-resistant metal oxide with a titaniumhalide, hydrolyzing the reaction product, contacting the driedhydrolyzate with an organoaluminum compound of the formula AlR X whereinR represents a hydrocarbon group, X represents a halogen atom and n is2-3, and thereafter eliminating said organo-aluminum compound.

Alumina may be used as the heat-resistant metal oxides of the presentinvention. The alumina is prepared by calcinating crystalline,low-crystalline or amorphous alumina hydrate at a temperature of about300 900 C. so as to effect dehydration. Silica or silica-alumina mayalso be used. Especially preferred is alumina prepared by subjecting alow-crystalline or amorphous alumina hydrate to heat treatment in thepresence of water '(this treatment will be referred to hereinafter ashydrothermal treatment") and calcinating the product at a temPerature ofabout 300 900 C. to effect dehydration. Saidhydrothermal treatment iscarried out at a temperature above 100 C., preferably at a temperatureabove l50 C. Generally, this treatment is carried out at a temperatureof 150 -350 C., with 200 300 C. being preferred. The time needed for thehydrothermal treatment is usually from minutes to 10 hours. However,this treatment may be carried out for a longer period of time. Ingeneral, the time needed for the hydrothermal treatment will decrease asthe temperature increases. Alumina hydrate subjected to the hydrothermaltreatment is calcined at 300 900 C., preferably at 400 700 C. to yielddehydrated alumina. Calcination for the dehydration of alumina hydrateis best carried out over a 1 hour period.

The heat-resistant metal oxide is reacted with a titanium halide.Titanium tetrachloride is preferably used from an industrial point ofview but other titanium halides such as titanium tetrabromide, titaniumtetraiodide may also be used.

The reaction between alumina and titanium halide is generally carriedout at a temperature ranging from 50 700 C. Where the reaction iscarried out at a temperature in the lower end of said range, unreactedtitanium halide may remain in the reaction product. Therefore, when thereaction is carried out at a temperature below 300 C. it is desirable toheat the reaction product at a temperature above 300 C. in an inertgasatmosphere in order to complete the reaction. This reaction results in anew compound having a tetravalent titanium.

The reaction between theheat-resistant metal oxide and titanium halidecan be carried out by various methods. For example, when titaniumtetrachloride is employed as titanium halide, it is desirable to chargethe heat-resistant metal oxide into a vertically constructed reactor andto introduce a stream of inert gas carrying titanium tetrachloride fromthe bottom of the reactor whereby the reaction proceeds whilemaintaining the heat-resistant metal oxide in a fluidized state. Anotherreaction mode is when the heat-resistant metal oxide is immersed intoliquid titanium tetrachloride and then heated.

The reaction product of the heat-resistant metal oxide with a titaniumhalide is hydrolyzed in an aqueous medium to yield the hydrolyzate whichcontains substantially no residual halogen. The hydrolyzing treatmentcan be carried out by any conventional method. For example, thehydrolysis can be achieved by merely boiling in water the reactionproduct of the heat-resistant metal oxide and the titanium halide. Whenammonia water or the like is used, hydrolysis is carried out readily atordinary temperatures.

The activity of the catalysts employed in the process of this inventionis seriously affected by the residual amount of halogen in thehydrolyzate. The catalytic activity often decreases as the amount ofresidual halogen increases. On hydrolysis, therefore, it is desirable toprepare the hydrolyzate by eliminating halogen as much as possible. Theatomic ratio of halogen to titanium in the hydrolyzate is preferably 0.1or less. When non-volatile salts are formed by hydrolysis as by using anaqueous sodium hydroxide solution for hydrolysis treatment, it isimportant that the product be washed sufficiently with water.

The thus-prepared hydrolyzate, substantially free of residual halogen,is reduced by contacting same with an organoaluminum compound to formthe catalyst. It is best to dry the hydrolyzate beforehand at atemperature below l,00O C., preferably at a temperature between 300 700C. If drying is not accomplished, the organoaluminum compound will bepartly decomposed, thus precluding the possibility of preparing acatalyst having good activity. On the other hand, if drying is carriedout at a temperature above l,000 C., the hydrolyzate will be denaturedthereby also precluding the possibility of preparing an active catalyst.

The organoaluminum compound, capable of reducing the hydrolyzate uponcontact, is represented by the general formula AIR X wherein Rrepresents a hydrocarbon group, X represents a halogen atom and n is2-3. Examples of these organoaluminum compounds include, for example,trialkyl-aluminums such as dimethylaluminum, triethylaluminum,tripropylaluminum, triisobutylaluminum, tri-n-octylaluminum, etc;dialkylaluminum monohalides such as dimethylaluminum monohalide,diethylaluminum monohalide, dipropylaluminum monohalide,diisobutylaluminum monohalide, di-n-octylaluminum monohalide,ethylisobutylaluminum monohalide, etc. or a mixture of said compounds.Trialkylalurninums and dialkylaluminum monohalides containing otheralkyl groups or a mixture of said com pounds can be employed equallywell. As the halogen, either chlorine, bromine or iodine can beeffectively used.

Reduction of the hydrolyzate is carried out by using the above describedorganoaluminum compounds. The reduction is carried out at a temperaturebelow 150 C., preferably at a temperature below C., by contacting thehydrolyzate with the organoaluminum compound. If the reductiontemperature exceeds C., the desired catalytic activity will not beachieved.

The contact time varies according to the reduction temperature, theconcentration of organoaluminum compound, the mode of contact, etc. butgenerally a contact time of from several minutes to one hour issufficient. Contact for a long period of time,say, over one hour, isgenerally not necessary save for the case where reduction is carried outat a lower temperature or with a lower concentration.

In the reduction reaction, the organoaluminum compound may be used assuch but an appropriate inert hydrocarbon may be used as a diluent toinsure a thorough contact.

The necessary quantity of the organoaluminum compound varies accordingto the organoaluminum compounds used. In general, the preferred quantityis 0.03 or more, with a quantity of at least 0.1 being most preferred,in terms of the atomic ratio of MIT i based on T1 present in thehydrolyzate. Taking into account impurities and other factors such as inthe case when a diluent is used, the organoaluminum compound is employedin an amount such that the ratio of Al/T i is 0.1 to 1.0. When the ratioof Al/T i is less than 0.03, it becomes impossible to obtain an activecatalyst. Although no upper limit exists for the ratio, an excessivelylarge quantity of organoaluminum compound is not desirable because nofurther enhancement in catalytic activity can be expected andfurthermore an excess of organoaluminum compound makes its removaldifficult.

After the reduction step it becomes necessary to separate theorganoaluminum compound from the catalyst. Upon separation from thecompound, the free organoaluminum compound must be removed substantiallyintact from the catalyst by means of operations such as filtration,washing, distillation, etc. When removal is not complete and theorgano-aluminum compound remains in the catalyst, the catalytic activitywill be lowered. Lowering of the catalytic activity will be manifestedin the case of a polymerization being carried out at 100 C. or more,particularly above 150 C.

In accordance with this invention, the polymerization of olefins iscarried out by using the catalyst as prepared above. Olefins which canbe used for the polymerization reaction include ethylene, propylene,butene-l and the like. It is also possible to copolymerize a mixture ofsaid olefins.

The polymerization reaction is carried out by dispersing the catalystinto an inert solvent, adding an olefin thereto and maintaining themixture at a given temperature and pressure.

Examples of the inert solvents include saturated hydrocarbons. N-hexane,n-heptane and cyclohexane are preferred but other solvents generallyused for the polymerization of olefins may be used. The reaction iscarried out at a relatively low temperature and pressure; the reactiontemperature is within the range from room temperature to 300 C.,preferably within the range from 50 250 C. The reaction pressure iswithin the range from to 200 kglcm preferably within the range from to100 kg/cm.

When the polymerization of olefins is carried out in accordance with theprocess of this invention, hydrogen may be present in the reactionsystem to control the molecular weight of the resulting polyolefins. Theamount of hydrogen present will vary according to the polymerizationconditions and the desired molecular weight of polyolefin. A partialpressure of hydrogen of 0.1 500 percent of the partial pressure ofethylene is sufficient; l0 100 percent is generally preferred.

Insofar as the catalyst used in the process of the present invention isreadily deactivated by moisture, oxygen, etc., the reactant materialssupplied to the polymerization system such as olefin, hydrogen andsolvent are preferably those which have been previously refined bydehydration and deoxygenation. During the reaction, dehydrating anddeoxygenating reagents may be present so as to further refine theolefin, hydrogen and solvent. The dehydrating and deoxygenating reagentsinclude alkali metals, alkali metal hydrides and the like.

The catalyst of the present invention has a high catalytic activitycompared with the catalysts used heretofore. The resulting polymers orcopolymers of olefins are linear crystalline polymers having highmolecular weights and are widely used as tough, colorless shapedarticles of high density.

EXAMPLE 1 130 g of commercially available alumina trihydrate prepared byBayer process (hydrargillite) were charged into a vertically constructedglass reactor. The particle size was 30-100 The alumina hydrate wascalcined at 500 C. in a stream of dry nitrogen. While the temperaturewas maintained at 375 C., a dry nitrogen gas carrying titaniumtetrachloride was passed through a titanium tetrachloride saturator andthen introduced into the lower end of the reactor. The reaction wascarried out for 2 hours. During the reaction, the temperature of thetitanium tetrachloride saturator was maintained at 63 C. and the feedrate of the nitrogen gas at the inlet was kept at 140 cm/minute (linearvelocity) so as to form fluidized layers in the reactor. The quantity oftitanium tetrachloride used for the reaction was 54 ml. After completionof the reaction, dry nitrogen gas was introduced for 10 minutes to expelthe remaining titanium tetrachloride and then the reaction product ofalumina and titanium tetrachloride was discharged from the lower end ofthe reactor.

50 g of this reaction product were immersed into 500 ml of 1 percentammonia water to effect neutralization and hydrolysis. The hydrolyzatewas then thoroughly washed with water to eliminate residual chlorine andthen dried at C. A chemical analysis of the hydrolyzate showed that itwas a new compound composed of titanium, aluminum and oxygen, containing3.24 percent by weight of titanium with no chlorine present.

2 g of the hydrolyzate were charged into a vertically constructed glassreactor and dried at 600 C. in a stream of argon. After drying, thehydrolyzate was contacted at a temperature of 30 C. with 50 ml oftriethylaluminumcyclohexane solution (concentration: 27 m-mol/liter) for10 minutes to effect reduction. Prior to the reduction reaction, theatomic ratio of MIT i was 1.0. After the reduction was completed, theproduct was washed thoroughly with cyclohexane (which had beendehydrated and deoxygenated) until triethylaluminum was no longerdetected in the washing solution. After washing, the product wascompletely dried with dry argon gas.

The above washing and drying treatments were all carried out at 30 C.

50 mg of the catalyst prepared as described above and 50 ml ofdehydrated and deoxygenated cyclohexane were introduced into a one-literautoclave. The air in the autoclave was replaced with high puritynitrogen and the autoclave was then heated and maintained at 180 C.Gaseous ethylene containing 12 percent hydrogen was introduced into theautoclave while stirring. The polymerization was carried out for 30minutes under a constant pressure of 40 kg/cm (total pressure) to obtain35 g of polyethylene having an average molecular weight of 85,000 and adensity of 0.967.

EXAlvfPLE 2 200 g. of commercially available low-crystalline aluminahydrate (Neobead C-MS; particle size 120 30 r; Mizusawa Kagaku) and 1.3liters of water were charged into a 2-liter autoclave. The mixture wasthen subjected to a hydrothermal treatment at 250 C. for 2 hours toobtain about g of pseudo-boehmite. 100 g of the resultingpseudo-boehmite were calcined at 400 C. The treatment was otherwisesimilar in every respect to the one described in Example 1. A newcompound composed of titanium, aluminum and oxygen and containing 1 1.2percent by weight of titanium was obtained.

From 2 g of the hydrolyzate thus obtained, the catalyst was preparedaccording to a process identical with that described in Example 1, using50 ml of triethylaluminumcyclohexane solution (concentration: 93m-mol/liter). The polymerization of ethylene was carried out underreaction conditions described in Example 1, utilizing 50 g of theprepared catalyst. 1 10 g of polyethylene having an average molecularweight of 95,000 and a density of 0.967 were obtained.

EXAMPLE 3 A series of catalysts were prepared as per the method ofExample 1, except that the concentration of the triethylaluminumcyclohexane solution was varied as shown in Table 1. Using thesecatalysts, the polymerization of ethylene was carried out under reactionconditions identical to those described in Example 2. The results areshown in Table 1.

TABLE 1 Concentration Atomic of triethylratio of Velocity of aluminumAl/T i at polymeriza- Average solution the time of tion (g.EP/ molecularNos. (m-mol/liter) reduction g. Cathr) weight From the tabulated resultsit is evident that when the ratio of Al/T i is less than 0.03 it isdifficult to obtain a catalyst having high activity and that an increasein the ratio of Al/T i does not afford a proportional increase incatalyst activity.

EXAMPLE 4 The polymerization of ethylene was carried out as described inExample 2, except that the reduction temperature of the hydrolyzate wasvaried as shown in Table 2.

ln cases where the reduction temperature exceeded 100 C., isoparaffinsof high boiling points were used in place of From the above-tabulatedresults, it is evident that where the reduction temperature exceeds 150C., satisfactory catalytic activity cannot be achieved.

EXAMPLE 5 A series of catalysts were prepared as per the method ofExample 2 except that the drying temperature of the hydrozylate wasvaried as shown in Table 3. The polymerization of ethylene was thencarried out under reaction conditions identical to those described inExample 2. The results are shown in Table 3.

TABLE 3 Drying Velocity of Average temperature polymerization molecularNos. C.) (g. EP/g. Cat.hr.) weight EXAMPLE 6 A series of catalysts wereprepared as per the method described in Example 2 except that theorganoaluminum compound was varied as shown in Table 4. Thepolymerization reaction was then analogously carried out as described inExample 2 and the results are shown in Table 4.

TABLE 4 Velocity of Average Organoaluminum polymerization molecular Nos.compounds (g.EP/g.Cat.hr.) weight Ex. 2 AI(C,H,,) 4400 95,000 Al( iso-Cl'ln )5 5100 101,000

2 Al(C,,H 4900 98,000 3 KCH ZQQ 4800 91,000 4 AI(C,H,,),C1 2500 99.000 5A1(c,H, ,1 2300 102,000 6 mgr-1 050011001 2600 88,000

EXAMPLE 7 A series of catalysts were prepared as per the method ofExample 3 except that triethylaluminum was replaced by diethylaluminummonochloride as shown in Table 5. The polymerization of ethylene wasthen carried out as described in Example 3. The results are shown inTable 5.

in Example 2 except that the proportion of hydrogen in theethylene-hydrogen mixture was varied as shown in Table 6. The resultsare shown in Table 6.

The proportion of hydrogen in the mixture of gases is expressed in termsof a mean value of H lethylene (mol ratio) by making analysis at thetime of polymerization on the vapor phase gases in the autoclave.

TABLE 6 Velocity of Average Pi /ethylene polymerization molecular Nos.(mol (g. EP/g. Cat.hr.) weight EXAMPLE 10 Substituting a gaseous mixtureof ethylene, propylene and hydrogen instead of a gaseous mixture ofethylene and hydrogen in the procedure described in Example 2, thecopolymerization of ethylene and propylene was carried out as in Example2. A copolymer having an average molecular weight of 97,000 and adensity of 0.951 was obtained. An IR- absorption spectrum analysis ofthe copolymer thus obtained showed that the copolymer was anethylene-propylene copolymer having branched methyl groups of 2.8 per1,000 carbon atoms.

In this copolymerization reaction, the result of an analysis made on thevapor phase gases in the autoclave at the time of polymerization showedthe-following average composition:

Ethylene 87 mol Propylene 1 mol Hydrogen 12 mol COMPARATIVE EXAMPLE Acatalyst was prepared as per the method of Example 2 except that afterthe reduction, the triethylaluminum cyclohexane solution was removedonly by filtration with no washing treatment. The polymerization ofethylene was carried out using this catalyst. The result is shown inTable 7 below.

TABLE 7 Velocity of Polymerization Washing treatment (g. EP/g. Cat. hr.)

No 100 Yes 4400 (Example 2) The result tabulated above apparently showsthat when an organoaluminum compound remains in the catalyst,satisfactory polymerization activity cannot be achieved.

It is to be understood that the term crystalline alumina hydrate refersto an alumina hydrate which shows a particular peak when analyzed by anX-ray diffraction apparatus; the term amorphous alumina hydrate" as usedherein for the hydrothermal treatment means an alumina hydrate whichdoes not show any particular peak and that the term low crystallinealumina hydrate" means an alumina hydrate which shows a definite peakbut the peak width is quite broad.

What is claimed is:

l. A catalyst, for the polymerization of olefins, prepared by reacting ahydrothermally treated alumina with a titanium halide to form a reactionproduct, said alumina being produced by heating a low crystalline oramorphous alumina hydrate at a temperature of more than 100 C. in thepresence of water and then calcining it at a temperature of about300-900 C. to dehydrate it; hydrolyzing the reaction product to form ahydrolysate containing substantially no residual halogen; drying saidhydrolysate at a temperature below l,00O C.; and reacting the driedhydrolysate with an organo-aluminum compound at a temperature below 150C., the ratio of aluminum atoms in the organo-aluminum compound totitanium atoms in the hydrolysate being at least 0.03 in terms of Al/Ti.

2. The catalyst as claimed in claim 1 wherein anY unreactedorgano-aluminum compound is removed.

3. The catalyst as claimed in claim 1 wherein the hydrolysis of thereaction product is carried out in an aqueous medium and the titaniumhalide is titanium tetrahalide.

4. The catalyst according to claim 1 wherein the reaction of the driedhydrolysate with the organo-aluminum compound is carried out at atemperature of from room temperature to 100 C.

5. The catalyst according to claim 1 wherein the ratio of aluminum atomsin the organo-aluminum compound to titanium atoms in the hydrolysate is0.1 1.0 in terms of MIT i.

6. A catalyst, for the polymerization of olefins, prepared by reactingat a temperature of 50-700 C. a titanium tetrahalide with ahydrothermally treated alumina to form a reaction product said aluminabeing produced by subjecting an alumina hydrate selected from the groupconsisting of lowcrystalline alumina hydrate and amorphous aluminahydrate to hydrothermal treatment at a temperature above 100 C. and thencalcining the hydrothermally treated alumina hydrate at a temperature of300- 900 C. to dehydrate it; hydrolyzing the reaction product in anaqueous medium to obtain a hydrolysate; drying said hydrolysate at atemperature below 1,000 C; reacting the dried hydrolysate at atemperature below 150 C. with an organo-aluminum compound of the generalformula AlR,,X; wherein R represents a hydrocarbon group, X represents ahalogen atom and n is 2-3, and then removing any unreactedorgano-aluminum compound.

7. The catalyst according to claim 6 wherein the organo-aluminumcompound is represented by the formula AJR X R represents an alkyl grouphaving one 12 carbon atoms, X represents a halogen atom having an atomicweight greater than 35 and n is 2-3.

8. The catalyst according to claim 6 wherein the organO- aluminumcompound is a trialkyl aluminum.

9. The catalyst according to claim 6 wherein the organo-aluminumcompound is a dialkyl aluminum mono-chloride.

10. The catalyst accordinG to claim 6 wherein said hydrothermaltreatment is carried out at a temperature of from 150-350 C; saidhydrothermally treated alumina hydrate is calcined at a temperature of400-700 C.; said reaction product is hydrolyzed in aqueous ammonia toobtain a hydrolysate wherein the ratio of chlorine atoms to titaniumatoms in said hydrolysate is less than 0.1 in terms of Cl/T i andwherein said hydrolysate is dried at a temperature of 300-700 C.

1 1. A process for the polymerization of olefins, which comprises thesteps of polymerizing said olefins, in an inert hydrocarbon, at atemperature ranging from room temperature to 300 C., under a pressure ofl0-200 atm, and in the presence of hydrogen, with a catalyst produced byreacting a hydrothermally treated alumina with a titanium halide to forma reaction product, said alumina being produced by heating a lowcrystalline or amorphous alumina hydrate at a temperature of more thanC., in the presence of water and then calcining it at a temperature ofabout 300-900 C. to dehydrate it; hydrolyzing the reaction product toform a hydrolysate containing substantially no residual halogen; dryingthe hydrolysate at a temperature below l,000 C.; reacting the driedhydrolysate with an organo-aluminum compound at a temperature below C.,the ratio of aluminum atoms in the organo-aluminum compound to titaniumatoms in the hydrolysate being at least 0.03 in terms of Al/T i; andthen removing unreacted organo-aluminum compound.

12. The process according to claim 11 wherein the partial pressure ofhydrogen is l-500 percent of the partial pressure of said olefins.

13. The process according to claim 11 wherein the polymerization isconducted at a temperature of 5 0-250 C.

14. The process according to claim 11 wherein said olefins are selectedfrom the group consisting of ethylene and ethylene containing a smallamount of propylene.

2. The catalyst as claimed in claim 1 wherein anY unreactedorgano-aluminum compound is removed.
 3. The catalyst as claimed in claim1 wherein the hydrolysis of the reaction product is carried out in anaqueous medium and the titanium halide is titanium tetrahalide.
 4. Thecatalyst according to claim 1 wherein the reaction of the driedhydrolysate with the organo-aluminum compound is carried out at atemperature of from room temperature to 100* C.
 5. The catalystaccording to claim 1 wherein the ratio of aluminum atoms in theorgano-aluminum compound to titanium atoms in the hydrolysate is 0.1 -1.0 in terms of Al/Ti.
 6. A catalyst, for the polymerization of olefins,prepared by reacting at a temperature of 50*-700* C. a titaniumtetrahalide with a hydrothermally treated alumina to form a reactionproduct said alumina being produced by subjecting an alumina hydrateselected from the group consisting of low-crystalline alumina hydrateand amorphous alumina hydrate to hydrothermal treatment at a temperatureabove 100* C. and then calcining the hydrothermally treated aluminahydrate at a temperature of 300*-900* C. to dehydrate it; hydrolyzingthe reaction product in an aqueous medium to obtain a hydrolysate;drying said hydrolysate at a temperature below 1,000* C; reacting thedried hydrolysate at a temperature below 150* C. with an organo-aluminumcompound of the general formula AlRnX3 n wherein R represents ahydrocarbon group, X represents a halogen atom and n is 2-3, and thenremoving any unreacted organo-aluminum compound.
 7. The catalystaccording to claim 6 wherein the organo-aluminum compound is representedby the formula AlRnX3 n, R represents an alkyl group having one - 12carbon atoms, X represents a halogen atom having an atomic weightgreater than 35 and n is 2-3.
 8. The catalyst according to claim 6wherein the organO-aluminum compound is a trialkyl aluminum.
 9. Thecatalyst according to claim 6 wherein the organo-aluminum compound is adialkyl aluminum mono-chloride.
 10. The catalyst accordinG to claim 6wherein said hydrothermal treatment is carried out at a temperature offrom 150*-350* C; said hydrothermally treated alumina hydrate iscalcined at a temperature of 400*-700* C.; said reaction product ishydrolyzed in aqueous ammonia to obtain a hydrolysate wherein the ratioof chlorine atoms to titanium atoms in said hydrolysate is less than 0.1in terms of Cl/Ti and wherein said hydrolysate is dried at a temperatureof 300*-700* C.
 11. A process for the polymerization of olefins, whichcomprises the steps of polymerizing said olefins, in an inerthydrocarbon, at a temperature ranging from room temperature to 300* C.,under a pressure of 10-200 atm, and in the presence of hydrogen, with acatalyst produced by reacting a hydrothermally treated alumina with atitanium halide to form a reaction product, said alumina being producedby heating a low crystalline or amorphous alumina hydrate at atemperature of more than 100* C., in the presence of water and thencalcining it at a temperature of about 300*-900* C. to dehydrate it;hydrolyzing the reaction product to form a hydrolysate containingsubstantially no residual halogen; drying the hydrolysate at atemperature below 1,000* C.; reacting the dried hydrolysate with anorgano-aluminum compound at a temperature below 150* C., the ratio ofaluminum atoms in the organo-aluminum compound to titanium atoms in thehydrOlysate being at least 0.03 in terms of Al/Ti; and then removingunreacted organo-aluminum compound.
 12. The process according to claim11 wherein the partial pressure of hydrogen is 1-500 percent of thepartial pressure of said olefins.
 13. The process according to claim 11wherein the polymerization is conducted at a temperature of 50*-250* C.14. The process according to claim 11 wherein said olefins are selectedfrom the group consisting of ethylene and ethylene containing a smallamount of propylene.